As a technology of removing deposits, for example, particles or contaminants, deposited on a surface of a substrate (hereinafter, referred to as “wafer”) as a target object, for example, a semiconductor wafer, there are known methods described in, for example, Patent Documents 1 and 2. In Patent Documents 1 and 2, it is described that a gas cluster ion beam is irradiated onto a surface of the wafer. In this technology, in order to overcome adhesive strength of the deposits to the wafer, for example, a physical shearing force of the gas cluster ion beam is adjusted by an acceleration voltage or an ionized amount.
However, along with miniaturization of a device structure formed on a wafer, the device structure can be easily damaged by a gas cluster ion beam. That is, by way of example, when a gas cluster ion beam is irradiated to a pattern having grooves and lines on a wafer, if a width of the line is, for example, several tens nm order, there is a risk that the line may be damaged by the irradiation of the gas cluster ion beam. Further, even if the pattern is not formed, after the gas cluster ion beam is irradiated, a surface shape of the wafer may be deteriorated.
Patent Document 3 describes a technology of removing a natural oxide film on a substrate with a chemical liquid and jetting air applied with ultrasonic vibration, and Patent Document 4 describes a technology of irradiating a pulsed laser onto a surface of a substrate. However, in Patent Documents 3 and 4, there is no description about removal of particles from a miniaturized device structure or damage to a wafer.